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The 2002 Überlingen midair collision

259 points| vinnyglennon | 2 years ago |admiralcloudberg.medium.com | reply

119 comments

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[+] omnibrain|2 years ago|reply
The plane crash storyline in Breaking Bad seems to be in part inspired by this event.

Having lived in the are and going to school in Überlingen at the time it is not something I'm ever going to forget.

I did not notice the crash itself (I'm a deep sleeper) but heard about it in the radio at morning. First I thought I must have misheared. Being a vonlunteer firefighter in our village I wondered, why I did not get an alarm. On my way to the train station I stopped at our local fire station but saw only a small transporter was missing, so I figured they may have alarmed only a few people.

There was some sort of "fog of war". Nobody knew anything for sure. There were rumours, that one of the planes crashed into the lake. The crash site being at Hohenbodman did not help because there is a village named Bodman on the other side of the lake.

Waiting for the train and on the train there was nothing else we could talk about. Arriving in Überlingen, we (a classmate and I) went straight down to the lakeside of the city to see if we can catch a glimpse of anything. The atmosphere in the city was surreal.

The route from the city center and train station to our school went over the yard of the city's fire station. And there it hit. Dozens of firefighters, police, red cross, etc. swarmed the place. A search dog unit just arrived. The facial expressions of everybody.

At school there was no lessons of course. Everybody just talked about the crash and the newest rumours. Some classmates arrived by bus and their bus drove straight by the crashsite. They saw corpses under cloth and smoking debris. A few hours later people from the local newspaper arrived to distribute a special issue with the most comprehensive compilation of available information at the time.

(... a few months later ...)

We had local festivities and I helped. It was bigger festivities and we spent days building everything and had to gather stalls, building material and tools from various storage areas, companies, etc. To fetch something I went with someone to a local building company. We went into their warehouse and an overwhelming stench of kerosene hit me. The warehouse was filled with transport container trays full of excavated ground that was contaminated with kerosine (and small debris) from the crash. The guy I went with just mentioned this in a very non-chalant way.

[+] leipert|2 years ago|reply
I was on vacation at Lake Constance that night. We didn’t hear anything consciously, but _everyone_ (four people) was awake at the time of the crash (unlikely, right?) and heading to the toilet/grabbing a water.

Next day we knew why we all were awake at the same time. Surreal.

[+] stall84|2 years ago|reply
Posts like this painfully push me to finish setting up my blog where I'm going to mostly opine on and outline aviation incidents like this..

But I can disseminate at least two flying maxims you can take away from this tragedy:

1: Do what TCAS is telling you to do.

2: Air Traffic Control does NOT have the final responsibility for your plane, you do.

- The TCAS system had already resolved the safe and correct conflict avoidance maneuvers for both of the transceivers involved (on both aircraft).

- As amazing and professional as our air traffic controllers are (and they are), they to, just like you the pilot are prone to error, and they in fact are not inside your aircraft, nor are they the pilot in command.

I've seen especially in new pilots and people that want to learn to fly this urge to defer to ATC (I even asked a friend who's a huge Flight Simulator enthusiast, of which I was too when young, what he'd do in a purely technical flight situation, and he responded he'd "ask ATC what to do"...).

While yes, Air Traffic Control 'controls' certain air space, they don't control your aircraft or its occupants. FAR 91.3 says it all, I'll let you look it up, it's 2 very brief (thank you FAA/congress) sentences that spell out the end of this discussion. You might get a fine, you might lose your license, etc etc, if you're reasoning for having to deviate from ATC rules aren't sufficient..

But hey in this case would those pilots on those 2 planes in this incident have rather lost their licenses (potentially) or have what happened happen.

Of course this incident is nuanced, as they all are. Flying safely involves mitigating and accepting certain levels of risk. TCAS was a system specifically designed and implemented to resolve collision situations. You test your equipment at regular intervals and pre-flight so that you can be confident they are working properly so that when you get into a situation where TCAS is telling you to do something, you do it.

But the reality is stress, human behavior isms' like maybe say flying in from an eastern european country and wanting to not 'piss off' the Swiss controllers, so deferring to their every direction instead of following your own instruments. << That's a real thing .. when you fly into busy airspace in the US, you quickly realize you just 'don't want to piss anyone off' .. All of these factors influence what should have been a cut and dry collision avoidance dictated by the TCAS system. And this is the cost of human flight.

[+] bfeynman|2 years ago|reply
I find this type of writing compelling, so if you write a blog I think you would get people to read it. One thing I've seen after the fact is the schism between media and evidence which adds an extra dimension here with the air traffic controller's story. The post mortem investigation usually takes a long time, and by then the media has completely moved on. Reminds me of the Boeing MCAS incidents, which interestingly I had a few airline industry friends, and internally according to them almost incidents were due inadequate training of pilots, but no one would say that since there is a nationalistic aspect to it.
[+] kingofpandora|2 years ago|reply
At the time there was no guidance to pilots on whether to follow TCAS or ATC.

That guidance to always follow TCAS came in because of this incident.

[+] krisoft|2 years ago|reply
> 1: Do what TCAS is telling you to do.

Other similar maxim is "In case you are intercepted by a fighter jet, and ATC and the fighter jet issues seemingly conflicting instructions follow what the fighter jet says/signals, and inform about this fact the ATC."

People with missiles trained on you have command priority for all the obvious reasons.

[+] stavros|2 years ago|reply
FAR 91.3:

(a) The pilot in command of an aircraft is directly responsible for, and is the final authority as to, the operation of that aircraft.

(b) In an in-flight emergency requiring immediate action, the pilot in command may deviate from any rule of this part to the extent required to meet that emergency.

(c) Each pilot in command who deviates from a rule under paragraph (b) of this section shall, upon the request of the Administrator, send a written report of that deviation to the Administrator.

[+] pwesner|2 years ago|reply
Did not expect this story on hackernews. I witnessed the crash. It was such a surreal moment…

Its the first time I read an article about all the details. Thanks for the writeup!

[+] distortionfield|2 years ago|reply
You witnessed the crash? Care to elaborate on that? Sounds very interesting!
[+] throwawaylinux|2 years ago|reply
Sorry to hear that. Must be be a heavy thing to carry.
[+] cobaltoxide|2 years ago|reply
"In 2004, Peter Nielsen, the air traffic controller on duty at the time of the collision, was murdered in an apparent act of revenge by Vitaly Kaloyev, a Russian citizen whose wife and two children had been killed in the accident."

https://en.wikipedia.org/wiki/2002_%C3%9Cberlingen_mid-air_c...

Jesus

Also:

"On 8 November 2007, Kaloyev was released from prison on parole after having served two-thirds of his sentence, a total of three and a half years."

"Returning to his home in North Ossetian city of Vladikavkaz, Kaloyev was met with enthusiastic crowds who cheered him as a hero."

[+] olliej|2 years ago|reply
Yup, murdered the only person involved in the collision that didn't actually cause it. Celebrated as a hero because "honor" is achieved by murdering an unarmed man who didn't kill your family, rather than the people in charge of the airline and ATC company that did. After all honor is defined by many as "murdering someone, regardless of what they did".
[+] MattRix|2 years ago|reply
The article covers this at some length.
[+] csours|2 years ago|reply
> The way this particular segment of Russian society reacted to the crash and the murder was an ugly reflection of a national tendency to blame whoever happens to be present at the moment of a tragedy, while those responsible for creating the unsafe condition go unnamed and unpunished.

Severe Tangent:

It's difficult to change the way you perceive the world, but I invite you to try.

Lately I've been thinking about how we understand and talk about tragedies and atrocities in history. Atrocities are traced back to who is most to blame, but not the conditions that led to the situation, not the political techniques that were used to gain the power, and certainly not how it might apply to ourselves.

When we find someone to blame for evil acts, we can close that mental box. That was the person who did it; I would never do something like that; I would never support someone like that.

But, most of the time, the evil leader did not start their reign with huge atrocities. It may have started with a fight that many of their followers did support.

It's easy to say "I would never support an atrocity", and maybe even say "I would never support someone who talks about any group as less than human".

The problem is, it's always easier to see this in your opponents than in yourself. I'm not making a false equivalence or an excuse; I'm saying it's really difficult and we should not be surprised when it is difficult. When the group mentality gets to a certain point, any reasonable nudge or criticism is taken as an attack.

I don't know of a great solution, but I think about how cult members are de-programmed. They have to remember or find something in the real world that they value. There has to be a bridge, not a demand that they renounce their beliefs.

[+] olliej|2 years ago|reply
Literally the whole point of NTSB and similar investigations is to find the cause of accidents, and this article is almost entirely sourced from those reports.

The person who decided I must blame someone, decided to murder the controller (that the report did not blame) and be celebrated as a hero by a bunch of moronic "manliness" "strong men" in Russia. This BS concept of "manliness" and "being strong" == "being better" needs to be stopped, and it's frustrating to see so much revival and promotion for it on YouTube and the like.

[+] banannaise|2 years ago|reply
I also found that quote very odd, for similar reasons. My immediate question was:

Why is this treated as a specifically Russian tendency?

The mindset sounds intimately familiar to me as an American. Many people, perhaps even most, operate on that idea. Our politics are heavily dependent on that idea. It also heavily underpins our justice system.

[+] rossdavidh|2 years ago|reply
Admiralcloudberg is, you know, never really a pick-me-up story kind of place, but this one is particularly grim.

Among many other things, a reminder that software upgrades need to be carefully planned, with an assumption that other stuff might go wrong while the system is offline.

[+] FabHK|2 years ago|reply
What is somewhat encouraging while reading the (grim) narratives of aviation accidents is this: how much has to go wrong for things to go seriously wrong (compare James Reason's Swiss Cheese model of accidents), and how most similar cases end well.

In this case, things that went wrong - and any one of them not going wrong might have averted the disaster:

1. Kids missed the original plane and had to get on this special charter flight instead. 2. Skyguide had just the previous year reduced staff from 3 to 2 controllers at night, and 2'. One of the controllers took an unofficial break. 3. There was an unexpected delayed A320 coming in, distracting the single controller. 4. The Tupolev was equipped with TCAS - if it hadn't been, TCAS on the other plane would not have issued an RA, and they might have stayed level or climbed instead of descending, as instructed by TCAS. (Though without TCAS it would not have been allowed to fly in Europe, probably.) 5. ATC happened to tell the Tupolev to descend, and TCAS happened to tell the 757 to descend. 6. That ATC instruction came exactly at the same time as the TCAS instruction on the 757, so the 757 crew didn't hear the ATC instruction to the Tupolev. 7. The Tupolev crew did not acknowledge that ATC instruction (which the 757 crew might have heard). 8. A bit later ATC repeated the instruction, and exactly at the same time TCAS on the 757 also repeated the instruction, so again they didn't hear the ATC instruction to the Tupolev. 9. Just then, the delayed A320 called ATC again, so the controller was distracted and did not monitor that his instruction to descend resolved the conflict successfully. 10. The copilot in the 757 had to go to the toilet just 18 seconds before all this happened. 11. It was night, making visual separation harder, possibly. 12. The 757 crew was trained to prioritise TCAS > ATC, the Tupolev crew was more or less trained to prioritise ATC > TCAS. 13. The Tupolev crew following ATC over TCAS received an ATC instruction that was in line with their right-of-way rules (left plane climbs, right plane descends), so it must have seemed more plausible. 14. The Tupolev crew had a first officer that suggested following TCAS instead, but he was not sitting in the RHS because there happened to be an extra Instructor Captain on that flight in the RHS who chose to follow ATC. 15. There happened to be a software upgrade at Zuerich ATC that night that disabled the Short-Term Conflict Alert light. 16. That software upgrade also disabled the phone lines, forcing the controller to waste time with the phone when trying to call Friedrichshafen for the delayed A320, and also prevented Karlsruhe ATC from warning Zuerich ATC of the problem. 17. ATC made a small, per se inconsequential, mistake of confusing "at your 2 o'clock" with "at your 10 o'clock". 18. The 757 crew waited 23 seconds to tell ATC that they were in a TCAS RA descent, by which time ATC was busy with the delayed A320. 19. The Tupolev crew was too busy/distracted to hear and understand that 757 TCAS RA descent call. 20. The ATC radar updated only every 12 seconds and did not yet reflect the 757's descent when ATC decided to instruct the Tupolev to descend. 21. The serious incident earlier in Japan with ATC/TCAS mismatch had not yet filtered through to all crews worldwide.

It's just so unlikely.

[+] alistairSH|2 years ago|reply
ATC communication is fascinating to me. I go down the Youtube rabbit hole a few times a month.

A few things that always stand out to me... - the calm demeanor shown by both ATC and pilots. Even in situations that make me cringe sitting at my laptop, everybody involved is steady. I know it's their job, but it still amazes me.

- the complexity of airport operations at a major international is mind-boggling. Hand-offs from ground to tower to departure... and then back again if something goes wrong. And doing that for dozens of planes at a time. Some crewed by pilots with thick accents or static-y radios.

- that air travel is the safest form of transit given the complexity of engineering and human processes involved is truly astounding. I know today's successes are the result of all previous tragedies; it's still something else.

I live under the main international approach to IAD. Watching the heavies fly in makes me smile. Especially the A380. It's a shame the A380 didn't find a long-term market - looking up, it shouldn't be able to fly, but there it is.

[+] BrentOzar|2 years ago|reply
> the calm demeanor shown by both ATC and pilots

My ex-wife was a US air traffic controller, and the training they go through is stunning. They're tested continuously for years, with something like an 80% wash-out rate.

During testing, they get 1-2 tests per week, working a shift just like a controller would, with fake pilots on the radio, and real computer systems. If they let airplanes get even remotely close to each other, they fail. If it happens twice, they're out of the FAA, immediately, permanently. One of the instructors told me, "It's my job to make sure your wife has the worst week of her career, every week, during training - so that when she's actually on the job, every week will seem easy no matter what she's facing."

Even just in training, you could see the stress take its toll on the candidates over the years.

[+] pc86|2 years ago|reply
As they say, every regulation is written in blood. An exaggeration for sure, but not by much. Many regs can point to a specific, not always fatal crash or series of incidents as the reason it exists.
[+] banannaise|2 years ago|reply
> A few things that always stand out to me... - the calm demeanor shown by both ATC and pilots. Even in situations that make me cringe sitting at my laptop, everybody involved is steady. I know it's their job, but it still amazes me.

disclaimer: I might be talking out my ass

It really seems that crisis response is bimodal. Either you almost completely panic, or you're almost completely focused. Complete focus makes for very clear, focused communication. (Extensive training on procedures, communication, and not panicking certainly helps as well.)

[+] didntknowya|2 years ago|reply
idk there's plenty of black box recordings of pilots panicking when a crash is imminent. ATC controllers on the other hand have training and physically don't have much to lose.
[+] jcranmer|2 years ago|reply
> the calm demeanor shown by both ATC and pilots. Even in situations that make me cringe sitting at my laptop, everybody involved is steady. I know it's their job, but it still amazes me.

It's actually probably not as amazing as it seems. I was just on a high ropes course, and it's similar to ATC in that if things go pear-shaped, there is just nothing that you can do. So when I saw something going wrong [1], the instinct I had to immediately run and try to help was suppressed, and instead I (and everybody else) was essentially in the same calm-and-collected mood.

[1] Admittedly, this is wrong in the "abnormal operation" sense, not "immediate risk to life" sense.

[+] ogig|2 years ago|reply
Ok, last week or so it was posted another long read blog post from Admiralcloudberg. Somebody commented that the rest of her posts were very nice. So true, I went into rabbit hole mode, been reading the rest avidly, just a few to go. Be warned!

PS: Tonight I dreamt of a surreal MD-80 crash.

[+] EdwardDiego|2 years ago|reply
AdmiralCloudberg is well worth supporting on Patreon IMO.
[+] PetitPrince|2 years ago|reply
As the article highlights with the Japan near-miss, "Regulations are written in blood". What a tragic story for everyone involved.
[+] jandrese|2 years ago|reply
That anecdote about the Japanese 747 near miss that required a dive so hard it sent a drink cart through the ceiling and injured nearly a quarter of the crew and passengers is also shocking. That's the reason you keep your seatbelt on even when the captain turns off the sign.
[+] gok|2 years ago|reply
If you'd like to feel extra uncomfortable next time you get on an airplane, read a bit more about limitations of TCAS that still exist today. For example, it doesn't actually model aircraft performance, so TCAS occasionally issues resolution advisories that are not physically possible. It also does not integrate with terrain awareness, so sometimes to avoid a collision with an aircraft it may suggest flying into a mountain (pilots are instructed to ignore TCAS RAs in this situation).
[+] Sebb767|2 years ago|reply
> pilots are instructed to ignore TCAS RAs in this situation

I like that you explicitly pointed out that flying into a mountain is not the recommended course of action for pilots.

Humor aside, this crash also includes a lot of broken down communication, so in most cases, even if TCAS fails, a crash is not inevitable. A pilot aware of the priority TCAS has will definitely communicate a failure to abide by its orders.

[+] FabHK|2 years ago|reply
Have these limitations ever been a problem in practice? As long as one plane climbs and the other doesn't, the conflict should be resolved, no?
[+] Retric|2 years ago|reply
Fixing either of those comes at significant risk because you are making the TCAS system significantly more complicated and it needs to work across multiple manufacturers and equipment build decades apart.
[+] banannaise|2 years ago|reply
> (pilots are instructed to ignore TCAS RAs in this situation)

Specifically, the ground proximity warning (as well as the stall warning) takes precedence over TCAS. This is just fine, since the "descend" aircraft in ground proximity will level off while the other climbs. You're not likely to find a condition where neither plane can deviate because the descender gets a ground proximity warning and the ascender gets a stall warning at the same altitude, since those are typically associated with aircraft flying close to their minimum and maximum altitude, respectively. You would need to have two aircraft flying level very close to the ground, at least one of them near its stall speed, which simply is not a flying condition used by commercial airliners.

[+] ilyt|2 years ago|reply
In this case it appears it would've worked just fine
[+] pc86|2 years ago|reply
This is a real issue, especially for GA aircraft in hard IMC at low altitudes, but airliners almost never receive RAs because they're almost never close enough to, especially enroute.
[+] dav_Oz|2 years ago|reply
While TCAS priority was the technical point of failure, I feel that the transition phase from public to private of the Swiss air traffic control services in 2001 seems to be the greatest disruption of this finely coordinated ATC.

Under the new management of Skyguide which led to the obvious cut in labor cost like reducing the night shift from 3 to 2 controllers. The private company still tolerated the extended break convention during night shift from before but leaving only one person responsible, now. And guess what? Maybe a software update to make some efficiency steps when we are at it. The single one controller was then informed during the update taking place what was still functioning and not which was very little.

>Part way through Nielsen’s shift, a group of technicians arrived to install the update, and he was informed that his work station’s main computer would have to be shut down, causing his displays to operate in fallback mode — a secondary condition in which several features provided by the main computer became unavailable. In fallback mode, the system which automatically correlated an aircraft’s radar return with its filed flight plan would not work, forcing him to enter the information manually, and the Short-Term Conflict Alert light, which illuminates when the system predicts that two planes will pass too close, would be rendered inoperative. But Nielsen had no idea what features would be lost in fallback mode, nor did he have any obvious way of finding out. And as if that wasn’t enough, a few minutes later the technicians informed him that they would also have to disconnect the control center’s direct telephone landline to neighboring centers

For me also surprisingly shocking that back in Karlsruhe multiple (!) controllers had to literally watch the obvious horror unfold while the one controller responsible was not available because of ... maintenance work.

>Heartbreakingly, controllers in neighboring Karlsruhe saw the collision coming, but they did not have the authority to speak to planes in another sector without permission from the responsible controller. The Karlsruhe controllers tried several times to call Nielsen in the minute before the crash, but the landlines were down and they couldn’t get through. By the time they gave up on this effort, it was too late to prevent the crash even by breaking the rules. The controllers were forced to watch, helpless, as the two planes collided and then disappeared from radar, knowing that dozens of people were dying before their eyes, and that there was nothing they could do to save them.

Edit: According to this article [0] and this verdict [1] the controllers in Karlsruhe had the full authority but were illegally instructed otherwise by DFS (German ATC) management which had an informal agreement with Skyguide (Swiss ATC) over this border region.

In the end the heavily traumatized and retired controller Nielsen was brutally stabbed because the modern diffusion of responsibility of companies only operates on the culture of financial compensation and is blissfully ignorant of a desperate man losing his whole family trying to restore his honor. So, no apology before everything is settled accordingly.

[0]https://www.dw.com/de/deutschland-haftet-f%C3%BCr-fehler-der...

[1]https://research.wolterskluwer-online.de/document/2ceee0e8-5...

[+] kergonath|2 years ago|reply
> In the end the heavily traumatized and retired controller Nielsen was brutally stabbed because the modern diffusion of responsibility of companies only operates on the culture of financial compensation and is blissfully ignorant of a desperate man losing his whole family trying to restore his honor.

Well yeah. I’d still take innocent until proven guilty over any of the blood debt and honour killing cultures. Particularly when the victim sacrificed to restore someone’s “honour” is not responsible. Desperation is no excuse, and of course we should not base our judicial systems on it.

As usual, the real culprits got nothing. As usual, this is unacceptable and, as usual, nothing has been or will be done to change this.

[+] Sebb767|2 years ago|reply
Minor nitpick, but

> The single one controller was then informed during the update taking place what was still functioning and not which was very little.

According to the text you quoted, it's worse:

> But Nielsen had no idea what features would be lost in fallback mode, nor did he have any obvious way of finding out.

Nielsen never knew which systems were out of order. Given the apparent workload he was under, knowing that the collision warning was out of order probably would not have helped, but it seems that he didn't even know for sure that the system was down.

[+] antihero|2 years ago|reply
Is there not a point where ignoring what you’re allowed to do and doing what’s best if it prevents massive human catastrophe is the correct option regardless of personal consequences? Nobody is going to jail for saving hundreds of lives. The media outcry would likely prevent any job loss…or was it that their systems wouldn’t allow them?
[+] stavros|2 years ago|reply
Why was TCAS priority the point of failure? As I understood it, the TCAS said the correct thing to both aircraft, but the ATC overrode it in one, resulting in the accident.
[+] laydn|2 years ago|reply
Anyone know why the TCAS only instructs the two approaching aircraft to change altitude only, but not heading?
[+] MerelyMortal|2 years ago|reply
I met someone who says he helped develop TCAS, and that it decides which one to climb or descend based on the registration number.

I'm guessing that it does not issue turn instructions because it only gives a Resolution Advisory when a collision is imminent (otherwise they would be giving RAs all the time). At altitude, where the air is thinner, it is much easier for a plane to immediately climb or descend, planes turn very slowly when the air is thin.

[+] lisper|2 years ago|reply
Good answers in sibling comments, but for those who don't want to grovel through a lot of stackexchange answers here is the TLDR: There are two reasons:

1. When TCAS was originally developed, the direction information to the other aircraft was not very accurate, being obtained only via the TCAS antenna. Nowadays GPS information is transmitted via ADS-B and so it's much more accurate, but taking advantage of this would require a major redesign. It may happen eventually, but...

2. Aircraft can change altitude faster than they can change heading. Also, most aircraft can change pitch faster than they can roll, and they are longer and wider than they are high. So effecting enough altitude change to avoid a collision can be done faster than effecting enough heading change to do so.

[+] sgustard|2 years ago|reply
You could imagine if, in addition to obeying the altitude change, every plane began to turn rapidly to the right, it could only help the situation? As long as we all agree to turn right in case of a collision warning?
[+] sklargh|2 years ago|reply
I’m consistently amazed by how many aviation accidents are caused by errant human interaction with properly functioning or unused but safety-critical automated systems. This is a theme of almost every major airliner loss in the 2000s.
[+] olliej|2 years ago|reply
Oh this is the one where privatization of ATC killed a bunch of people, and then one asshole decided that it was ok to murder the one person involved who was explicitly not responsible. The responsible parties - as outlined in the report:

1. The Russian airline: it put untrained pilots in charge of a plane. We know they were untrained as they clearly did not understand the most basic concept of TCAS. The article tries to paint this is regulatory confusion - which is patently nonsense, the entire concept of TCAS hinges on it being on par with stall and terrain alerts, where there is a single response, and that response counters any other instruction. The fact that the pilots were aware of the system and failed to learn about it is a failure on their part, the fact that the airline company failed to have the most basic of training on it makes it mostly theirs.

2. The Skyguide company: understaffed a region, and then under equipped it while understaffed, and then failed to have any reasonable back up for anything. Arguably a failure brought on by those people that insist "privatizing a public safety system is efficient".

But then Mr Macho-man had to defend his honor by going and murdering the one remaining victim of the crash, to demonstrate how manly he was. If you feel that murdering an innocent and defenceless person is justified for the "honor" of your family, and to give you value as a "man" I say you've failed the most basic tenets of "honor", and sure as shit don't get to brag about manliness.

[+] Fissionary|2 years ago|reply
> the one person involved who was explicitly not responsible

Not to condone revenge killings, but Nielsen was obviously part of this accident. It was his choice to work alone that night (rather than waking the other controller) and to allow the technicians to turn off most of his instruments, so the responsibility is partly his. He also issued the fateful descend command - had he literally stayed out of this, the Tupolev pilots would have followed the TCAS guidance and the accident would not have happened.